Cellular respiration is the metabolic process by which cells convert biochemical energy from nutrients, primarily glucose, into adenosine triphosphate (ATP), the usable energy currency of the cell. This process involves the oxidation of food molecules using an electron acceptor, typically oxygen in aerobic respiration, and releases waste products such as carbon dioxide and water
. The overall process can be divided into several key stages:
- Glycolysis: Occurs in the cytoplasm, where one glucose molecule (6 carbons) is broken down into two molecules of pyruvate (3 carbons each). This step produces a net gain of 2 ATP molecules and 2 NADH molecules, which carry high-energy electrons
- Pyruvate Oxidation: Pyruvate molecules enter the mitochondria and are converted into acetyl coenzyme A (acetyl-CoA), releasing carbon dioxide and generating NADH
- Citric Acid Cycle (Krebs Cycle): Acetyl-CoA enters this cycle in the mitochondrial matrix, producing ATP, NADH, and FADH2 while releasing carbon dioxide as a waste product
- Oxidative Phosphorylation (Electron Transport Chain): High-energy electrons from NADH and FADH2 are transferred through a series of proteins in the mitochondrial inner membrane, driving the production of a large amount of ATP. Oxygen acts as the final electron acceptor, forming water
Cellular respiration can be aerobic (requiring oxygen) or anaerobic (using other electron acceptors), with aerobic respiration yielding the most ATP. The energy released in this controlled process powers various cellular activities essential for survival, growth, and function
. In summary, cellular respiration is the biochemical pathway that cells use to break down glucose and other nutrients to produce ATP, enabling life- sustaining energy transformations
